State regulators say March gas explosion in Seattle originated from improperly abandoned gas line

SEATTLE — State safety regulators released a report on Tuesday saying the March 9 natural gas explosion in Seattle’s Greenwood neighborhood originated from an improperly abandoned gas line.

The Utilities and Transportation Commission filed a formal complaint against PSE citing 17 violations of pipeline safety regulations and recommended a penalty of $3.2 million.

The UTC’s Pipeline Safety team has been investigating the explosion that injured nine firefighters and caused extensive property damage.

According to the report:

"The investigation found the immediate cause of the explosion was outside force applied by unauthorized individuals to a gas service line owned by Puget Sound Energy. The damage allowed gas to escape, accumulate in the building occupied by Mr. Gyros restaurant, and ultimately explode.

The broken gas service line was one that PSE records showed as abandoned in 2004. At the time, PSE failed to properly disconnect and seal the line, allowing it to remain in service for nearly 12 years without proper oversight."

Lab tests confirmed that the line failed at the threaded connection "due to applied external force," according to the report.

"The gas service line that PSE believed was abandoned in 2004 was located in a space not intended for human occupancy between the Mr. Gyros and Neptune Coffee businesses. Evidence at the scene and witness interviews indicated that the space around the gas line was frequently used by unauthorized individuals to store personal items. Individuals acknowledged to investigators that due to the limited space, they sometimes disturbed the gas line to access the area."

PSE said Tuesday that the fine is "disappointing and excessive."

"The proposed fine from the state Utilities and Transportation Commission (UTC) staff is disappointing and excessive.

All parties investigating the March incident, including the UTC and the Seattle Fire Department, agree: the natural gas system at the Greenwood site was damaged by unauthorized individuals in a space not intended for human activity, with the resulting gas leak causing the explosion and fire.

While we disagree with the UTC staff’s conclusions and recommended fine, we’re committed to the safety of our customers and the community and will continue to review the report as we prepare for final disposition of this investigation by the UTC commissioners."

Investigators allege that PSE violated pipeline safety regulations by failing to:

  • Abandon a service line according to federal standards;
  • Follow its internal pipeline deactivation plan;
  • Perform annual leak surveys of an active service line;
  • Perform atmospheric corrosion tests of an active service line at least once every three years; and
  • Perform external corrosion tests of an active service line at least once every 10 years.

The state recommends that PSE be required to review all previously abandoned service lines and provide a plan for finding and mitigating any other unsuccessful line "retirements."